Too Few Firstborn?

“So Moses numbered all the firstborn among the sons of Israel, just as the Lord had commanded him;and all the firstborn males by the number of names from a month old and upward, for their numbered men were 22,273.” Numbers 3:42-43

“These are the numbered men of the sons of Israel by their fathers’ households; the total of the numbered men of the camps by their armies, 603,550.” Numbers 2:32

How could there only be 22,273 firstborns among a population of 603,550? The answer lies in the redemption price.

“For the ransom of the 273 of the firstborn of the sons of Israel who are in excess beyond the Levites,you shall take five shekels apiece, per head;” Numbers 3:46-47

“But if they are from a month even up to five years old, then your valuation shall be five shekels of silver for the male, and for the female your valuation shall be three shekels of silver.” Leviticus 27:6

22,273 firstborn is counting only the boys from one month to five years old.